Search

[PT] No passado recente, o grupo de investigação "Structural Composites" da Universidade do Minho e a empresa CiviTest – Pesquisa de Novos Materiais para a Engenharia Civil, Lda. têm realizado vários estudos experimentais e numéricos avançados, em parceria, que permitiram a aquisição de conhecimento e o desenvolvimento de materiais de matriz cimentícia reforçados com fibras recicladas (BRFR), nomeadamente as provenientes da indústria da reciclagem de pneus. A investigação desenvolvida tem evidenciado que as fibras recicladas possuem elevadas potencialidades como reforço efetivo do betão, nomeadamente no reforço ao corte. No presente trabalho pretende-se apresentar os resultados relativos à avaliação da eficácia do reforço ao corte de vigas em betão por intermédio da aplicação de finos painéis em microbetão auto-compactável reforçado com fibras de aço de pneus reciclados nas faces de vigas de betão armado existentes. Para tal foram efetuados ensaios comparativos de resistência ao corte entre vigas em betão armado de referência (viga I com 1.25 x 0.17 x 0.30 m3 ; alma com 0.09 m) e vigas similares reforçadas na alma com painéis de 2 cm de espessura em microbetão auto-compactável reforçado com fibras recicladas usando dois sistemas distintos de fixação às respetivas vigas em betão armado. A eficiência da aplicação dos referidos painéis em vigas demonstrou que é possível obter aumentos de capacidade de carga da ordem dos 250% em vigas não fendilhadas e em vigas previamente fendilhadas. Os resultados e conclusões obtidos são apresentados na presente publicação., Os autores agradecem a colaboração das empresas CiviTest – Pesquisa de Novos Materiais para a Engenharia Civil, Lda. (no apoio à realização dos ensaios experimentais), BioSafe e RECIPNEU (no fornecimento das fibras de aço recicladas para o reforço do betão).

The authors appreciate the collaboration of the following labs: Civitest for developing DHCC materials, PIEP for conducting VARTM process (Eng. Luis Oliveira) and Department of Civil Engineering of Minho University to perform the tests (Mr. Antonio Matos and Eng. Marco Jorge)., In this paper, a new generation of composite sandwich slab is proposed as a solution for the rehabilitation of slabs in old masonry buildings. An innovative solution was developed during this research formed by four components: a Deflection Hardening Cement Composite (DHCC) layer on the top compression skin, a glass fiber reinforced polymer (GFRP) skin at the bottom tension surface, GFRP ribs to transfer shear from top to bottom layers, and foam core for thermal-insolation purposes. The DHCC layer contributes significantly for the load carrying and deflection capacity due to its stiffness, compressive strength and toughness, offers resistance to the occurrence of buckling phenomena in the GFRP ribs, improves the performance of this structural concept against impact and fire, and constitutes an excellent medium for the application of finishing materials, like ceramics or timber. Two different hybrid composite slabs were developed and tested, and their behavior was assessed under flexural loading. The results showed that the developed hybrid sandwich slabs accomplish all design requisites for serviceability and ultimate limit states, and assure a stiffness/dead-weight and load-capacity/dead-weight ratios much higher than conventional structural slab systems., FCT - Fundação para a Ciência e Tecnologia

This research proposes the development of innovative structural sandwich panels composed of thin outer wythes of Sisal Fiber-Cement Composites (SiFCC) and a core layer of Polypropylene FiberReinforced Lightweight Concrete (PFRLC). Sisal fibers were used in two different lengths, short sisal fibers (50 mm) randomly distributed in the matrix; and long unidirectional aligned sisal fibers (700 mm) applied by a cast hand layup technique. Lightweight aggregates and polypropylene fibers were used in the concrete core to reduce panel’s density, to improve its thermal insulation and energy absorption, and to assure the required shear capacity. The behavior of the sandwich panels in four-point bending test is described and the various failure mechanisms are reported. Pull-off tests were performed to evaluate the bond strength between SiFCC and PFRLC layers. The results revealed that the long sisal fibers were more effective in terms of increasing the ultimate flexural capacity, exhibiting a deflection hardening and multiple cracking behavior, comparing with the SiFCC laminates reinforced with short sisal fibers, which presented a deflection softening response after first cracking. The panels with short sisal fibers (SSiFCC) revealed higher bond strength between the layers in comparison to the panels with long sisal fibers (LSiFCC)., The study reported in this paper is part of the activities carried out by the Authors within the International Cooperation Project “EnCoRe - Environmentally-friendly solutions for Concrete with Recycled and Natural components” (www.encore-fp7.unisa.it), funded by the European Union within the International Research Staff Exchange Scheme (IRSES) of the 7th Framework Programme (FP7PEOPLE-2011-IRSES, n.º 295283). The first author acknowledges the research grant under this project.

Publicado em "Proceedings of the 5th International Conference on The Concrete Future", ISBN 978-981-07-6067-0, For conventional concrete without steel fibers, although still an aspect under discussion, there are some commonly used durability indicators. However, for steel fiber reinforced self-compacting concrete (SFRSCC) literature is sparse and the aspects of durability, particularly corrosion resistance, still deserve deeper research, mainly the corrosion of the fibers, since its influence on the appearance and on the serviceability limit states of a SFRSCC structure can be a concern. Therefore, in the ambit of an ongoing research project dealing with the development of SFRSCC sandwich panels, durability tests were executed to compare the performance of SFRSCC and self-compacting concrete (SCC) specimens. Nine different tests were performed, applied to SFRSCC and SCC in order to characterize their mechanical properties (elasticity modulus, compressive strength and flexural behaviour) and to evaluate its durability indicators normally used for plain concrete, namely: water absorption by immersion and by capillarity, permeability to air, electrical resistivity, chloride diffusion by migration under nonsteady state and carbonation. The results for the different concretes and curing times up to 28 days are presented and analyzed., (undefined)

A three-year research project (Pontalumis) was carried out for the development of an innovative simply supported hybrid footbridge, with 11 m of length and 2 m of width. The footbridge is composed of two pultruded I-shaped glass fibre reinforced polymer (GFRP) girders (400×200(×15) mm2) bonded and bolted to a 37.5 mm thick deck in steel fibre reinforced self-compacting concrete (SFRSCC). The present paper describes the material/structural concept of this footbridge, its design and construction process, and summarizes the response of the prototype when submitted to static short and long-term load tests, and dynamic load tests. The prototype was simple and fast to execute, presenting a reduced dead-weight of only about 3 tonf. The static and dynamic behaviour of the prototype as well as its long-term deflection fulfil standards’ requirements for footbridge structures and are in good agreement with conventional analytical and numerical design tools., ADI